Wire drawing process and apparatus



' Feb. zo, 1945.

W. O. SCHULTZ WIRE DRAWING PROCESS AND APPARATUS Filed Feb. 10, 1943 yI5 Sheets-Sheet 1 Byfwz We m ATTORNEYS Feb. 20,v 1945. w. o. SCHUL-rzWIRE DRAWING PROCESS AND APiARATUS Filed Feb. V1o, 194s s sheets-sheet 2R i i i .i i

3 Sheets-Sheet 5 INVENTOR.

hg N @fm o@ M M .UWM WB Feb. 20, 1945. wl o, sc||u| 'rz WIRE DRAWINGPROCESS AND APPARATUS Filed Feb. 10. 1943 vmami mi. zo, i945 UNITEDSTATES PATENT orifice WIRE DRAWING PROCESS AND APPARATUS William' 0.Schultz, Scarsdale, N. Y., asslgnor to Crucible Steel Company ofAmerica, New York, `N. Y., a corporation o! New Jersey 4 ApplicationFebruary 10, 1943Serlal No. 475,366

' l (ci. 205-16) l2 Clalms.

The invention relates to the art of wire drawing, and especially to thereduction'by drawing e .of hot rolled alloy steels which are so hardenedby thermal treatment or mechanical working as to make them diilicult orimpractical to draw by usual methods. The principles of the inventionare also applicable to the reduction of such alloy steel bars to rodform by drawing operations instead of by hot rolling as heretofore, andwire or rod of special shapes other than circular may be produced. A

In reducing hot rolled steel rod down to drawn wire, the conventionalpractice has long been to cold-draw the rod and resulting wire insuccessive drafts to the gauge desired. An objection to this is thatfollowing only-relatively small re duction by each drawing step, thewiremust be subjected to a heat treatment in the nature of referred to,as to which the drawing operations have been difficult and impractical.

In a general way the invention aims to provide conditions of operationunder which diiilcult-todraw alloy steel wire may be successfully drawnin actual practice in such a way as to largely eliminate the objectionsattendant upon the customary cold drawing practices of the prior art,en-

. abling the diiIlcult-to-draw alloy steels to be satisfactorily andreliably drawn into wire or rod hardening aigZrieve the strainssufficiently for the ensuing r wing step to be satisfactorily performedwithin the temperature range above mentioned. The sub-critical strainrelieving treatment above referred to will be sufficient even in respectto the most diillcult-to-draw alloy steels such as tungsten ormolybdenum high speed steels, martensitic stainless steels, bearingsteels, or high carbon, high chromium die steels, and austeniticstainless steels such as 18-8 or 25-20, and likewise as to strainrelieving heat treatment if required after the final drawing step,unless a grain structure is desired which requires final heat treatmentat a higher temperature.y A. similar sub-critical strain relievingtreatment will be used preliminary to the first drawing step, unless thestock has been previously subjected to a strain relieving or annealingheattreatment.

A number of important practical requirements are satisfied by drawingalloy steels of the above type within the temperature range abovespeci.- fied, after the preliminary strain relieving treatment. Withinthis range the metal is hot enough and which lower temperatures fromthestand-f point of reduction obtainable in actual' practice and fromthe standpoint of avoidingy excessive form, at a cost many times lessthan heretofore,

and resulting inthe elimination of extra steps and the reduction ofexcessive strains in the metal such as have been attendant upon the colddrawing operations customarily used for steel wire.

I have discovered that the satisfactory drawing of elongated alloy steelstock of the above char- 'acter to secure the objectives ofthe'invention may be achieved by subjecting the stock between successivedrawing steps, to a sub-critical strain relieving treatment, followingwhich the stock is cooled or quenched to a temperature ranging strainsin the metal, afford no advantages as com'- pared to cold drawing. Ascompared yto substantially higher drawing temperatures, ,the range abovereferred .to avoids the danger of vundue loss of diameter enabling thewire to be pulled through at higher speed and with greater reduction.

A drawing temperature within the range above Vspecified also enableseffective lubrication to be securedv by a simple and inexpensivelubricant such as a graphitic lubricant consisting for example of byweight of graphite and 40% of finely divided clay as a binder. Such alubricant may be applied by spraying an aqueous suspension thereof onthe wire after the stock has been of thestock more than 20 or 30 degreesin passing.

to the drawing die, but at temperatures materially tubular retort ofFig. 3, and

2 l escasos higherthan the range above specified this type oflubrication becomes impractical, and the matter or providing properlubrication becomes much more expensive and diilicult at highertemperatures.

For successful operation it is important that the temperature to whichthe stock is heated, both during heat treatment and for the drawingoperation, be exceedingly constant as to all portions of the stockpassing through, and it is important that accurate and quicklyresponsive regulation and control of the temperature conditions beprovided. For these reasons I prefer to carry out the steps abovereferred to in successive heating apparatus having certain features ofconstruction as hereinafter described in greater detail, thestrain-relieving treatment being carried out preferably in a bath ofmolten lead or other suitablecomposition and the stock then passing to asecond bath of molten babbitt or the like having a melting point ofabout 400 F. and acting as a quenching bath to quickly cool the metalfed to it at the hotter temperature of from 9501300 F. down to atemperature of between 500-700 F. at which latter temperature 25 thequenching bath is constantly maintained. The metal being drawn'is thuskept under nondecarburizing and non-oxidizing conditions while passingto the die, which together with the moderate temperatures required,avoids scaling and 30 pitting.

As examples of alloysteels dimcult to cold draw, but which may be easilydrawn in accordance with the present invention, the following Theinvention is thus applicable in general to the hot drawing of alloysteels which are hardenable either thermally or by working, and which ithas been difficult and impractical to reduce by the conventional colddrawing practice. 55

In the drawingsv Figs, la and 1b and lc show in side elevation anassemblage of apparatus for drawing iron or steel rod and wire inaccordance with the invention, Fig. lb being an extension of la at X-X,and Fig. 1c an extension of Fig. 1b at YY,

Fig. 2 is a vertical section taken through a molten metal bath apparatusappropriate to be used in carrying out the heatingl treating and drawingoperations of Figs. 1b and 1c.

Fig. 3 is a section on line 3-3 of Fig. 2 looking, in the direction ofthe arrows.

Fig. 4 is an enlarged detail section through the Fig. 5 is a similarsection taken at right angles ltofthe section of Fig. 4.

"7. Fig. 6 is an enlarged side view partly in sec- '.tion of the drawingdie and pulling mechanism.

Fig. 7 is a plan view of the drawing die and Fig, 8 is a section on line3 3 of Fig. 6 look ing in the direction of the arrows.

Referring to the drawings, the rod or wire t to be drawn, is mounted inthe form of a coil on reel 2 on an unwinding drum 3 which is freelyrotatable on a spindle 4. The rod l is fed from the reel through a guidestand 5 consisting of an eyelet mounted on a support as shown. From theguide stand 5, the rod passes into the tubular retort or pipe-likecontainer 3, which is filled with molten lead as indicated at l, Fig. 2,this container being provided with upwardly extending goosenecked endsat the entrance and amt, as indicated at 3 and 9, to prevent the leadfrom flowing out, the lead rising to about the level ld in thegoosenecked portions as shown.

`The lead bath retort 8 is housed in a tubular furnace 122 consisting ofa metal base 23a, Fig.

3, built up of angle members as shown, supporting a hearth or licor 24and lateral walls 2d, 25 of refractory brick, the walls being surmountedby a semi-circular metal shell 2l lined with refractory brick 28. Theretort 6 is supported at spaced intervals upon transversely extendingbars welded thereto, which in turn extend into the side walls 25, 26.Also the upper portion of the retort 6 is slotted at intervals forreception of rounded bars 3| for submerging the rod or wire l beneaththe level of the lead bath in its passing therethrough.

Extending longitudinally of the furnace and resting on the hearth 24 isa fuel pipe or gas header 32 provided with uniformly spaced upstandingnipples, such as 33a, provided with burner tips, as at 34, these burnersbeing disposed beneath the retort 6 as shown.

For supplying the fuel mixture to the header or manifold 32, an injectorvalve 33 extends through the hearth and opens into the manifold. Theinjector valve 33 is fed from a source (not shown) over a. supply line34a, in which is interposed a motorized valve 35 operated by athermostatically controlled motor 36 for automatically regulating theburners in accordance with the temperature desired for the bath. Thisautomatic regulation is effected by meansV including a thermo-couplepyrometer 31 mounted in a protective tube 33 extending through the roofof the furnace and welded onto the retort 5to pro vide an openingthereinto for exposing the thermo-couple pyrometer to the temperature ofthe lead bath. From the pyrometer 31, appropriate electrical connections33a extend to a potentiometric indicating recorder 33, from whence inturn other appropriate electrical connections 40 extend to the motor 36controlling the valve 35, in a well-known manner, for operating thevalve in accordance with the temperature at which the lead bath is to beregulated.

For the purpose of accurately controlling the temperature of the rod orwire I, it is important that the thermo-responsive element 31 project inthrough the upper wall of the retort 3 into contact with the molten leadwhich is immediately in contact with the wire l, and it is importantthat the wire be held spaced from the upper wall of the retort,otherwise the temperature of different portions of the wire will not beuniform and the thermo element 3l will not respond accurately totemperature conditions in different parts of the wire.

The furnace 22 performs the subcritical strain-relieving step previouslydescribed, and the wire or rod thus heated to a temperature of 950-1300F. then passes to a heating apparatus 4I (Fig. 1c) which may beunderstood as exactly similar to the apparatus 22 previously v describedin connection with Figs. 2l to 5, except in heating apparatus 4|, andwhile the wire is passing from thence to the drawing die. As

`shown in Fig. lc, the lubricant may be applied to the wire in alubricating chamber 42 having apertured guides 43 for the wire or rod,and as the latter passes throughvchamber 42 it receives a coating of thelubricant which is sprayed thereon as at 44, by nozzles 45 to which anaqueous mix of the lubricant is supplied under pressure by pipe lines 4Bleading from a pump 41 connected to a reservoir 48 containing a supplyof the lubricant. The lubricating chamber 42 may be shaped as shown sothat excess lubricant will drain back to reservoir 48 through a returnpipe 49. As previously stated the lubricant preferably consists .of amixture of 60% graphite with 40% comminuted clay as a binder in aqueoussuspension.

The stock need not be materiallyl cooled by spraying of the lubricantthereon as above described, and sufcient space is left between thechamber 42 and the drawing die hereinafter described, to afford time forthe lubricant to dry on the surface of the stock before reaching thedie.

The rod or wire then passes to the drawing die 54 'which is shown asmounted in a die-box 55 illled lwith Babbitt metal 56 which ismaintained in molten condltionby means of a burner 51 fed from theinjector valve 52 by means of a fuel feed pipe 58, a suitable controlvalve 59 being provided to regulatethe heat and thus keep the die 54 atsubstantially the same temperature as the rod or wire passing throughit. This matter of heating the die to substantially the sametemperatureas the wire passing through it, is irnportant to the successof the drawing operation. The die-box is shown as mounted in a holdingframe 60, in'which it is clamped by a suitable screw 6 I As shown inFigs. 1c and 6. the wind-up drum 63 is provided with a series of hooks64 which are axially slidable with respect to the'drum for the purposelof receiving the overow of the wire being reeled up on the drum.Fastened to one end of a chain 65 having its opposite end secured to thedrum, is a clamp E6 which grips the wire being fed through the die.

It should be understood that successive drawing operations, eachinvolving a reduction of 2535% as above described, may be performeduntil the stock has been reduced lto the desired. diameter or otherdimensions, the strainrelieving and quenching operations being carriedout as above described preliminary to each successive drawing step. Theprocess thus lends itself to the production of wire in successive andcontinuous drawing steps. Referenceris here made vtn my earliercopending application Serial No. v 457,154 filed Sept. 3, 1942, and alsoto my earlier 75 rst bath, thereby to produce a temperaturebeapplication Serial ber 21, 1941.

While the invention has been disclosed ascarried out by apparatus of theabove described specinc construction, it should be understood that manychanges may be made therein without departing from the invention in itsbroader aspects, within the scope of the appended claims.

4 I claim:

1. The method of treating elongated alloy steel stock of thediillcult-to-draw types which are hardenable thermally, or by mechanicalworking, which includes progressively passing the same through a bathheated to atemperature near the critical, thereafter progressivelyquenching said stock by passing same through a bath of lower temperatureto reduce the temperature of the stock to -a value between about 50df700F., and

' drawing said stock through a die substantially at said last mentionedtemperature.

2. The method of treating elongated alloy steel stock of thedimcult-to-draw types which are hardenable thermally, or by mechanicalworking, which includes progressively subjecting the same to a strainrelieving heat treatment, thereafter quenching said stock by passingsame y through a, liquid heated to a temperature between about W-700 F.,and thereafter progressivelydrawing said stock through a die while ,saidstock is substantially at the temperature of said liquid.

3. The method of treating elongatedalloy steel stock of thedilcult-to-draw types which are hardenable thermally, or by mechanicalWorking, which includes passing the same through a bath prior to theapplication of lubricant thereto, regulating the temperature of saidbath to maintain same between about 500700 F., applying lubricant tosuch stock after passing through said bath, and drawing the lubricatedstock through 9, die at substantially the temperature of said bath.

4. The method of treating elongated alloy steel stock of thedifiicult-to-draw types which are hardenable thermally, or by mechanicalworking, which includes subjecting the same to a strain-relieving heattreatment, thereafter passing said stock progressively through a fluidmedium which is heated to a temperature ben tween about 500-700 F. tocool said stock subthrough a die while said stock is substantially atthetemperature of said fluid medium.

6. Apparatus of the class described for producing drawn elongated wireand like purposes, said apparatus including means for maintaining aliquid treating bath at a temperature near the critical point of saidstock, a drawing die, means interposed between said rst mentioned bathand said die for maintaining a second uid medium at a temperaturesubstantially lower than the Number 419,822. illed NovemVV tween about500-'100 s'. in the stock passing through said second mentioned fluidmedium. and means for drawing the stock successively through said bath,iluid medium, and said die.

7. Apparatus of the class described, for producing drawn elongated wireand like purposes, said apparatus including means for maintaining aliquid treating bath at a temperature near the critical point of saidstock, a drawing die, means interposed between said first mentioned bathand said die for maintaining a second treating bath at a temperaturesubstantially. lower than the first, to producefa temperature betweenabout 500-'700 F. in the stock leaving said second mentioned bath, andmeans for drawing the stock successively through said baths and saiddie, means being interposed between said second mentioned bath and saiddie for applying lubricant to the stock before it passes fto thedie.

8. Apparatus of the class described for producing drawn elongated wireand like purposes,

.said apparatus including a chamber having means associated therewithfor heatingthe stock to a temperature near its critical point, a drawingdie, means interposed between said chamber and said die for quenchingthe stock to a temperature between about 50G-'700 F. and mechanism fordrawing the stock successively through said chamber, said quenchingmeans and said die.

9. The method of treating elongated alloy steel stock of thedifficult-to-draw types.` which are hardenable thermally or bymechanical working, which includes progressively subjecting the stock toa heat treatment near the critical point of said stock, thereaftersuddenly cooling the stock from a temperature near the critical to atemperature several hundred degrees F. lower but above about 500 F.,said heat treating and cooling operations the stock to a heat treatmentnear the critical point ot said stock, thereafter suddenly cooling thestock from a temperature near the critical to a temperature severalhundred degrees F. lower but above about 500 F., said heat treating andcooling operations being conducted without intervening drawingoperations. and then progressively drawing the cooled stock through adie while said stock is still at a temperature above about 500 F., theaforesaid method ineluding the step of applying lubricant to said stockbetween the above mentioned heat treating and drawing operations.

11. Apparatus of the class described for producing drawn elongatedwireand like purposes, said apparatus including a chamber having meansassociated therewith for heating the stock toa temperature near itscritical point, a drawing die, means interposed between said chamber andsaid die for suddenly cooling the stock from a temperature near thecritical to a temperature several hundred degrees F. lower but aboveabout 500 F. and mechanism for drawing the stock f successively throughsaid chamber, said cooling being conducted without intervening drawingoperations, and theny progressively drawing the cooled stock through adie while said stock is still at a temperature above about 500 F.

10. The method o1' treatingv elongated alloy steel stock of thedimcult-to-draw types, which are hardenable thermally or by mechanicalworking, which includes progressively subjecting means and said die,said apparatus being con structed and arranged to maintain said stock ata" temperature above about 500 F. when passing to said die.

12. Apparatus of the class described for producing drawn elongated wireand like purposes, said apparatus including a chamber having meansassociated therewith for heating the stock to a temperature nearitscritical point, a drawing die, means interposed between said chamberand said die for suddenly cooling the stock from a temperature near thecritical to a temperature several hundred degrees F. lower but aboveabout 500 F., and mechanism for drawing the stock successively throughsaid chamber, said cooling means and said die, said apparatus beingconstructed and arranged to maintain said stock at a temperature aboveabout 500 F. when passing to said die and said apparatus including meansinterposed between said chamber and said die for applying lubricant tosaid stock.

WILLIAM O. SCHULTZ.

